Induction motors are widely used in a variety of application areas such as power generation systems, manufacturing units, factories, electronic appliances, and the like. Induction motors can experience a variety of faults such as drive-train failure, bearing faults, broken rotor bars faults. For example, broken rotor bars faults can cause the broken parts to hit stator windings at high velocity resulting in failures of the inductive motors. Therefore, there is a need to detect a fault in the induction motors to reduce the losses caused by such faults.
Different techniques for fault detection that are employed at present include, but are not limited to, vibration and acoustic noise analysis, electromagnetic field monitoring and axial flow measurement, temperature measurement, infrared recognition, and spectral analysis of stator current in the motor.
Conventionally, the monitoring of faults in induction motors has been mainly performed using vibration signals. The mechanical faults in rotor bars produce vibrations in radial rotor movement which in turn produce torque oscillations at the rotor mechanical rotating frequency. The monitoring and study of the rotor mechanical rotating frequency can lead to detecting mechanical faults associated with the rotor bars. However, condition monitoring using vibration signals has numerous disadvantages such as background noise due to external excitation motion, and sensitivity to the installation position.
Another technique of the fault detection methods is based on the analysis of the stator current. Such a technique is receiving increased attention in the detection of mechanical faults in electric machines due to offering significant economic savings and simple implementation, see, e.g., U.S. 2014/0303913. However, certain fault current signatures, such as ones observed for broken bar faults, are usually subtle compared to the dominant components in the sampled stator current such as a fundamental frequency of the power supply, eccentricity harmonics, and slot harmonics. Unlike vibration monitoring, for which industry standards have been developed from long-time field experience, the field experience in stator current monitoring is limited, and significant difficulties exist.
For example, the magnitude of fault signatures can vary at different loads even if the fault signatures in the stator current are already subtle. In addition, with broken bar fault detection, the signature frequency of broken bar fault in the stator current is close to the fundamental frequency of the induction motor. As a result, it can be difficult to distinguish fault signatures from the normal operation signatures, when rotor bars of the induction motor are faulty.
Therefore, there exists a need for a method and a system for detecting faults of in the induction motors based on current signature analysis.